The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale (odontocete) having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter. The now outdated synonym Physeter catodon refers to the same species. It is one of three extant species in the sperm whale superfamily, along with the pygmy sperm whale and dwarf sperm whale.

A mature male can grow to 20.5 metres (Template:Convert/ft)Template:Convert/test/A long. It is the largest living toothed animal. For large males, the head can represent up to one-third of the animal's length. It has a cosmopolitan distribution across the oceans. The species feeds primarily on squid but to some extent on fish, diving as deep as Template:Convert/kmTemplate:Convert/test/A, which makes it the deepest diving mammal. Its diet includes giant squid and colossal squid. The sperm whale's clicking vocalization is the loudest sound produced by any animal, but its functions are uncertain. These whales live in groups called social units. Units of females and their young live separately from sexually mature males. The females cooperate to protect and nurse their young. Females give birth every three to six years, and care for the calves for more than a decade. The sperm whale has few natural predators, since few are strong enough to successfully attack a healthy adult; orcas attack units and are capable of killing the calves. The sperm whale can live for more than 70 years.

Historically, the sperm whale was also known as the common cachalot; "cachalot" is derived from an archaic French word for "tooth". Over most of the period from the early 18th century until the late 20th century, the sperm whale was hunted to obtain spermaceti and other products, such as sperm oil and ambergris. Spermaceti found many important uses, such as candles, soap, cosmetics and machine oil. Due to its size, the sperm whale could sometimes defend itself effectively against whalers. In the most famous example, a sperm whale attacked and sank the American whaleshipEssex in 1820. As a result of whaling, the sperm whale is currently listed as vulnerable by the IUCN.

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The name sperm whale is an apocopation of spermaceti whale. Spermaceti, originally mistaken for the whales' "sperm", is the semi-liquid, waxy substance found in the spermaceti organ or case in front of and above the skull bone and also in the junk, the area below the spermaceti organ and just above the upper jaw.[3] The case consists of a soft white, waxy substance saturated with spermaceti oil. The junk is composed of cavities filled with the same wax and spermaceti oil and intervening connective tissue.[3][4][5]
The sperm whale is also known as the "cachalot", which is thought to derive from the archaic French for "tooth" or "big teeth", as preserved for example in cachau in the Gascon dialect (a word of either Romance[6] or Basque[7] origin). The etymological dictionary of Corominas says the origin is uncertain, but it suggests that it comes from the vulgar Latin cappula, plural of cappulum, sword hilt.[8] According to Encarta Dictionary, the word cachalot came to English "via French from Spanish or Portuguese cachalote, perhaps from [Portuguese] cachola, 'big head'". The term is retained in the Russian word for the animal, кашалот (kashalot), as well as in many other languages.

The sperm whales unique body is unlikely to be confused with any other species. The sperm whale's distinctive shape comes from its very large, block-shaped head, which is can be one-quarter to one-third of the animal's length. The S-shaped blowhole is located very close to the front of the head and shifted to the whale's left.[4] This gives rise to a distinctive bushy, forward-angled spray.

The sperm whale's flukes are triangular and very thick. The whale lifts its flukes high out of the water as it begins a feeding dive.[4] It has a series of ridges on the back's caudal third instead of a dorsal fin. The largest ridge was called the 'hump' by whalers, and can be mistaken for a dorsal fin because of its shape and size.[9]

In contrast to the smooth skin of most large whales, its back skin is usually wrinkly and has been likened to a prune by whale-watching enthusiasts.[16] Skin is normally a uniform grey in color, though it may appear brown in sunlight. Albinos have also been reported.[17][18][19]

The sperm whales' lower jaw is very narrow and underslung.[20] The sperm whale has 18 to 26 teeth on each side of its lower jaw which fit into sockets in the upper jaw.[20] The teeth are cone-shaped and weigh up to 1 kilogram (Template:Convert/LoffAonSoff)Template:Convert/test/A.[21] The teeth are functional, but do not appear to be necessary for capturing or eating squid, and well-fed animals have been found without teeth. One hypothesis is that the teeth are used in aggression between males.[22] Mature males often show scars which seem to be caused by the teeth. Rudimentary teeth are also present in the upper jaw, but these rarely emerge into the mouth.[23]

The sperm whale has adapted to cope with drastic pressure changes when diving. The flexible ribcage allows lung collapse, reducing nitrogen intake, and metabolism can decrease to conserve oxygen.[26][27]Myoglobin, which stores oxygen in muscle tissue, is much more abundant than in terrestrial animals.[28] The blood has a high red blood cell density, which contain oxygen-carrying hemoglobin. The oxygenated blood can be directed towards the brain and other essential organs only when oxygen levels deplete.[29][30][31] The spermaceti organ may also play a role by adjusting buoyancy (see below).[32]

While sperm whales are well adapted to diving, repeated dives to great depths have long term effects. Bones show pitting that signals decompression sickness in humans. Older skeletons showed the most extensive pitting, whereas calves showed no damage. This damage may indicate that sperm whales are susceptible to decompression sickness, and sudden surfacing could be lethal to them.[33]

Between dives, the sperm whale surfaces to breathe for about eight minutes before diving again.[4] Odontoceti (toothed whales) breathe air at the surface through a single, S-shaped blowhole. Sperm whales spout (breathe) 3–5 times per minute at rest, increasing to 6–7 times per minute after a dive. The blow is a noisy, single stream that rises up to 2 metres (Template:Convert/ft)Template:Convert/test/A or more above the surface and points forward and left at a 45° angle.[34] On average, females and juveniles blow every 12.5 seconds before dives, while large males blow every 17.5 seconds before dives.[35]

Early on it was proposed that the nasal complex, which includes the spermaceti organ, the junk bodies, and other associated organs, was used as a battering ram (see below)[39] or for buoyancy regulation (see below);[32][40] however, researchers' current understanding suggest that the primary function of the spermaceti organ and the associated organs in the nose of the sperm whales are used as part of the world's most powerful natural sonar system.[41][42][43][44][45][46][47][48][49]

Due light absorption by water, most of the ocean is dark beyond a few hundred meters thus limiting visual range. As a result, sperm whales and the other toothed whales (suborder odontoceti) have evolved a system of echolocation as the main way to find food in the darkness of the ocean similar to that used by bats to find food in the darkness of the night sky. When echolocating, the sperm whale emits a directionally focused beam of broadband clicks. Clicks are generated by the forcing of air through a pair of phonic lips (also known as "monkey lips" or "museau de singe") at the front end of the nose, just below the blowhole. The sound then travels backwards along the length of the nose through the spermaceti organ. Most of the sound energy is then reflected off an air sac which sits against the skull and down into the Junk Bodies, where the sound is focused by the junk's lens-like structure.[41][42][43][44][45][46][47][48] Some of the sound will reflect back into the spermaceti organ and back towards the front of the whale's nose where it will be reflect through the spermaceti organ a third time. This back and forth reflection which happens on the scale of a few milliseconds creates a multi-pulse click structure.[50] This multu-pulse click structure actually allows researchers to measure the whale's spermaceti organ using only the sound of its clicks and given the size of the spermaceti organ relates to the size of the whale, biologist can measure the whales be recording their echolocation clicks.[51][52] The lower jaw is the primary reception path for the echoes. A continuous fat-filled canal transmits received sounds to the inner ear.[53]

The spermaceti organs may also help adjust the whale's buoyancy. It is hypothesized that before the whale dives, cold water enters the organ, and it is likely that the blood vessels constrict, reducing blood flow, and, hence, temperature. The wax therefore solidifies and reduces in volume.[32][40] The increase in specific density generates a down force of about Template:Convert/NTemplate:Convert/test/A and allows the whale to dive with less effort. During the hunt, oxygen consumption, together with blood vessel dilation, produces heat and melts the spermaceti, increasing its buoyancy and enabling easy surfacing.[54] However, more recent work[44] have found many problems with this theory including the lack of anatomical structures for the actual heat exchange.[55]

Herman Melville's Moby Dick suggests that the "case" containing the spermaceti had evolved as a kind of battering ram for use in fights between males.[39] However, there are almost no modern accounts of fights between male sperm whales.[49] Apart from a few famous exceptions of the well-documented sinking of the ships Essex and Ann Alexander by attackers estimated to weigh only one-fifth as much as the ships, this hypothesis is not well supported in current scientific literature.[56]

It is relatively abundant from the poles to the equator and is found in all the oceans. It inhabits the Mediterranean Sea, but not the Black Sea,[9] while its presence in the Red Sea is uncertain.[2] The shallow entrances to both the Black Sea and the Red Sea may account for their absence.[57] The Black Sea's lower layers are also anoxic and contain high concentrations of sulphur compounds such as hydrogen sulphide.[58]

Sperm whales can live 70 years or more.[9][17][60] They are a prime example of a species that has been K-selected, i.e., their reproductive strategy is associated with stable environmental conditions and comprises a low birth rate, significant parental aid to offspring, slow maturation, and high longevity.[4]

How they choose mates has not been definitively determined. There is evidence that males have dominance hierarchies, and there is also evidence that female choice influences mating.[61]Gestation requires 14 to 16 months, producing a single calf.[9]Lactation proceeds for 19 to 42 months, but calves may suckle up to 13 years (although usually less).[9] Calves can suckle from females other than their mothers.[9] Females generally have birth intervals of three to six years.[9]

Females reach sexual maturity between 7 and 13 years; males follow beginning at 18 years. Upon reaching sexual maturity, males move to higher latitudes, where the water is colder and feeding is more productive. Females remain at lower latitudes.[9] Males reach their full size at about age 50.[4]

Females stay in groups of about a dozen individuals and their young.[4] Mature males leave their "natal unit" somewhere between 4 and 21 years of age. Mature males sometimes form loose "bachelor groups" with other males of similar age and size.[4] As males grow older, they typically live solitary lives.[4] Mature males have beached themselves together, suggesting a degree of cooperation which is not yet fully understood.[4]

The most common non-human attacker of sperm whales is the orca, but pilot whales and the false killer whale also sometimes harass them.[62][63] Orcas prey on target groups of females with young, usually making an effort to extract and kill a calf. Female sperm whales repel these attacks by encircling their calves. The adults either face inwards to use their tail flukes against the orcas, or outwards, fighting with their teeth.[4] This marguerite formation, named after the flower, is also used by whales to support an injured unit member. Early whalers exploited this behavior, attracting a whole unit by injuring one of its members.[64] If the orca pod is extremely large, its members may sometimes be able to kill adult female sperm whales. Large mature male sperm whales have no non-human predators, and are believed to be too large, powerful and aggressive to be threatened by orcas.[65]

An older study, examining whales captured by the New Zealand whaling fleet in the Cook Strait region, found a 1.69:1 ratio of squid to fish by weight.[70] Sperm whales sometimes steal Sablefish and Toothfish from long lines. Long-line fishing operations in the Gulf of Alaska complain that sperm whales take advantage of their fishing operations to eat desirable species straight off the line, sparing the whales the need to hunt.[71] However, the amount of fish taken is very little compared to what the sperm whale needs per day. Video footage has been captured of a large male sperm whale "bouncing" a long line, to gain the fish.[72] Sperm whales are believed to prey on the megamouth shark, a rare and large deep-sea species discovered in the 1970s.[73] In one case, three sperm whales were observed attacking or playing with a megamouth.[74]

The sharp beak of a consumed squid lodged in the whale's intestine may lead to the production of ambergris, analogous to the production of pearls.[75] The irritation of the intestines caused by squid beaks stimulates the secretion of this lubricant-like substance. Sperm whales are prodigious feeders and eat around 3% of their body weight per day. The total annual consumption of prey by sperm whales worldwide is estimated to be about Template:Convert/STTemplate:Convert/test/A — a figure greater than the total consumption of marine animals by humans each year.[76]

It is not well understood why the sperm whale's head is so large in comparison to the lower jaw. One theory is that the sperm whale's ability to echolocate through its head aids in hunting. However squid, its main prey, may have acoustic properties too similar to seawater to reflect sounds.[77] The sperm whale's head contains a structure called the phonic lips, also known as the monkey lips, through which it blows air. This can create clicks that have a source level exceeding 230 decibels re 1 micropascal referenced to a distance of 1 metre (Template:Convert/ft)Template:Convert/test/A – in other words it is by far the loudest sound made by any animal, and 10–14 dB louder than a powerful rifle sounds in air at 1 metre (Template:Convert/ft)Template:Convert/test/A away.[78] It has been hypothesised that clicks attempt to stun prey. Experimental studies attempting to duplicate this effect have been unable to replicate the supposed injuries, casting doubt on this idea.[79]

The sperm whale belongs to the orderCetacea, the order containing all whales and dolphins. It is a member of the suborderOdontoceti, the suborder containing all the toothed whales and dolphins. It is the sole extant species of its genus, Physeter, in the family Physeteridae. Two species of the related extant genus Kogia, the pygmy sperm whaleKogia breviceps and the dwarf sperm whaleK. simus, are either placed in this family, or in the family Kogiidae.[80] In some taxonomic schemes the families Kogiidae and Physeteridae are combined as the superfamily Physeteroidea (see the separate entry on the sperm whale family).[81]

The sperm whale is one of the species originally described by Linnaeus in 1758 in his 18th century work, Systema Naturae. He recognised four species in the genus Physeter.[82] Experts soon realised that just one such species exists, although there has been debate about whether this should be named P. catodon or P. macrocephalus, two of the names used by Linnaeus. Both names are still used, although most recent authors now accept macrocephalus as the valid name, limiting catodon's status to a lesser synonym.[a]

Fossil sperm whales differ from modern sperm whales in tooth count and the shape of the face and jaws.[85] For example Scaldicetus had a tapered rostrum.[86] Genera from the Oligocene and early and middle Miocene, with the possible exception of Aulophyseter, had teeth in their upper jaws.[85]Acrophyseter, from the late Miocene, also had teeth in both the upper and lower jaws as well as a short rostrum and an upward curving mandible (lower jaw).[81] These anatomical differences suggest that fossil species may not have necessarily been deep-sea squid eaters like the modern sperm whale, but that some genera mainly ate fish.[85]Zygophyseter, dated from the middle to late Miocene and found in southern Italy, had teeth in both jaws and appears to have been adapted to feed on large prey, rather like the modern Orca (Killer Whale).[77]

The traditional view has been that Mysticeti (baleen whales) and Odontoceti (toothed whales) arose from more primitive whales early in the Oligocene period, and that the super-family Physeteroidea, which contains the sperm whale, dwarf sperm whale, and pygmy sperm whale, diverged from other toothed whales soon after that, over 23 million years ago
.[83][85] In 1993–1996 molecular phylogenetics analyses by Milinkovitch and colleagues, based on comparing the genes of various modern whales, suggested that the sperm whales are more closely related to the baleen whales than they are to other toothed whales, which would have meant that Odontoceti were not monophyletic, in other words did not consist of a single ancestral toothed whale species and all its descendants.[88] However more recent studies, based on various combinations of comparative anatomy and molecular phylogenetics, criticised Milinkovitch's analysis on technical grounds and re-affirmed that the Odontoceti are monophyletic.[88][89][90]

Spermaceti, obtained primarily from the spermaceti organ, and sperm oil, obtained primarily from the blubber in the body, were much sought after by 18th, 19th, and 20th century whalers. These substances found a variety of commercial applications, such as candles, soap, cosmetics, machine oil, other specialized lubricants, lamp oil, pencils, crayons, leather waterproofing, rust-proofing materials and many pharmaceutical compounds.[91][92][93][94]Ambergris, a solid, waxy, flammable substance produced in the digestive system of sperm whales, was also sought as a fixative in perfumery.

Prior to the early 18th century, hunting was mostly by indigenous Indonesians.[95] Legend has it that sometime in the early 18th century, around 1712, Captain Christopher Hussey, while cruising for right whales near shore, was blown offshore by a northerly wind, where he encountered a sperm whale pod and killed one.[96] Although the story may not be true, sperm whales were indeed soon exploited by American whalers. Judge Paul Dudley, in his Essay upon the Natural History of Whales (1725), states that one Atkins, ten or twelve years in the trade, was among the first to catch sperm whales sometime around 1720 off the New England coast.[97]

There were only a few recorded catches during the first few decades (1709-1730s) of offshore sperm whaling. Instead sloops concentrated on Nantucket Shoals where they would have taken right whales or went to the Davis Strait region to catch bowhead whales. By the early 1740s, with the advent of spermaceti candles (before 1743), American vessels began to focus on sperm whales. The diary of Benjamin Bangs (1721–1769) shows that, along with the bumpkin sloop he sailed, he found three other sloops flensing sperm whales off the coast of North Carolina in late May 1743.[98] On returning to Nantucket in the summer 1744 on a subsequent voyage he noted that "45 spermacetes are brought in here this day," another indication that American sperm whaling was in full swing.[98]

American sperm whaling soon spread from the east coast of the American colonies to the Gulf Stream, the Grand Banks, West Africa (1763), the Azores (1765), and the South Atlantic (1770s). From 1770 to 1775 Massachusetts, New York, Connecticut, and Rhode Island ports produced 45,000 barrels of sperm oil annually, compared to 8,500 of whale oil.[99] In the same decade the British began sperm whaling, employing American ships and personnel.[100] By the following decade the French had entered the trade, also employing American expertise.[100] Sperm whaling increased until the mid-19th century. Spermaceti oil was important in public lighting (for example, in lighthouses, where it was used in the United States until 1862, when it was replaced by lard oil, in turn replaced by petroleum) and for lubricating the machines (such as those used in cotton mills) of the Industrial Revolution. Sperm whaling declined in the second half of the 19th century, as petroleum came in to broader use. In that sense, it may be said to have protected whale populations from even greater exploitation.[101][102] Sperm whaling in the 18th century began with small sloops carrying only one or two whaleboats. The fleet's scope and size increased over time, and larger ships entered the fishery. In the late 18th century and early 19th century sperm whaling ships sailed to the Pacific, the Indian Ocean, Japan, the coast of Arabia, Australia and New Zealand.[100][103][104] Hunting could be dangerous to the crew, since sperm whales (especially bulls) will readily fight to defend themselves against attack, unlike most baleen whales. When dealing with a threat, sperm whales will use their huge head effectively as a battering ram.[105] Arguably the most famous sperm whale counterattack occurred on November 20, 1820, when a whale claimed to be about 25.9 metres (Template:Convert/ft)Template:Convert/test/A long rammed and sank the Nantucket whaleship Essex. Only 8 out of 21 sailors survived to be rescued by other ships.[106] This instance is popularly believed to have inspired Herman Melville's famous "Moby Dick".[107]

The sperm whale's ivory-like teeth were often sought by 18th and 19th-century whalers, who used them to produce inked carvings known as scrimshaw. Thirty teeth of the sperm whale can be used for ivory. Each of these teeth (up to 8 inches long and 3 inches across), are hollow for the first half of their length. Like walrus ivory, sperm whale ivory has two distinct layers. However, sperm whale ivory contains a much thicker inner layer. Though a widely practiced art in the 19th century, scrimshaw using genuine sperm whale ivory declined substantially after the retirement of the whaling fleets in the 1880s. Currently the Endangered Species Act and CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, prevents the sales of or trade in sperm whale ivory harvested after 1973 or in scrimshaw crafted from it.

Modern whaling was more efficient than open-boat whaling, employing steam-powered ships and exploding harpoons. Initially, modern whaling activity focused on large baleen whales, but as these populations were taken, sperm whaling increased. This was especially true during World War II when spermaceti, the fine waxy oil produced by sperm whales, was in high demand for lubricating the American war machine. In both the 1941-2 and 1942-3 seasons, the Norwegian expedition took over 3,000 sperm whales off the coast of Peru alone. After the war whaling continued unabated to obtain oil for cosmetics and high-performance machinery, such as automobile transmissions.

The hunting led to the near extinction of large whales including sperm whales until bans on whale oil use were instituted in 1972.International Whaling Commission gave the species full protection in 1985. Hunting by Japan in the northern Pacific Ocean continued until 1988.[102]

It is estimated that the historic worldwide population numbered 1,100,000 before commercial sperm whaling began in the early 18th century.[2] By 1880 it had declined by an estimated 29 per cent.[2] From that date until 1946 the population appears to have recovered somewhat as whaling pressure lessened, but after the Second World War, the population declined even further, to only 33 per cent of the pre-whaling era.[2] It has been estimated that in the 19th century between 184,000 and 236,000 sperm whales were killed by the various whaling nations,[108] while in the modern era, at least 770,000 were taken, the majority between 1946 and 1980.[109]

Sperm whales increase the levels of primary production and carbon export by depositing iron rich faeces into surface waters of the Southern Ocean. The iron rich faeces causes phytoplankton to grow and take up more carbon from the atmosphere. When the phytoplankton dies, it sinks to the deep ocean and takes the atmospheric carbon with it. By reducing the abundance of sperm whales in the Southern Ocean, whaling has resulted in an extra 2 million tonnes of carbon remaining in the atmosphere each year.[110]

Remaining sperm whale populations are large enough that the species' conservation status is rated as vulnerable rather than endangered.[2] However, the recovery from the whaling years is a slow process, particularly in the South Pacific, where the toll on breeding-age males was severe.[111]

The number of sperm whales throughout the world is unknown, but is thought to be in the hundreds of thousands.[2] The conservation outlook is brighter than for many other whales. Historically, Japan has taken ten sperm whales a year, and until 2006 tens of these whales were hunted off Indonesia. They are protected practically worldwide, and commercial whaling has ceased.[2] Fishermen do not target the creatures that sperm whales eat.[2] However, long-line fishing operations in the Gulf of Alaska have complained about sperm whales stealing fish from their lines.[71]

Entanglement in fishing nets and collisions with ships represent the greatest threats to the sperm whale population currently.[17] Other current threats include ingestion of marine debris, ocean noise, and chemical pollution.[112] The IUCN regards the sperm whale as being "vulnerable".[2] The species is listed as endangered on the United States Endangered Species Act.[113]

The species is listed on Appendix I[114] and Appendix II[114] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I[114] as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. It is listed on Appendix II[114] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. It is also covered by the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region
(Pacific Cetaceans MOU).

Rope-mounted teeth are important cultural objects throughout the Pacific. In New Zealand, the Māori know them as "rei puta" and were rare because sperm whales were not actively hunted in traditional Māori society.[115] Whale ivory and bone were taken from beached whales. In Fiji the teeth are known as tabua and they were traditionally given as gifts for atonement or esteem (called sevusevu), and were important in negotiations between rival chiefs.[116]Friedrich Ratzel in The History of Mankind reported in 1896 that, in Fiji, whales' or cachalots' teeth were the most-demanded article of ornament or value. They occurred often in necklaces.[117] Today the tabua remains an important item in Fijian life. The teeth were originally rare in Fiji and Tonga, which exported teeth, but with the Europeans' arrival, teeth flooded the market and this "currency" collapsed. The oversupply led in turn to the development of the European art of scrimshaw.[118]

Herman Melville's novel Moby-Dick is based on a true story about a sperm whale that attacked the whaleship Essex.[119][120] Melville associated the sperm whale with the Bible's Leviathan.[120][121] The fearsome reputation perpetuated by Melville was based on bull whales' ability to fiercely defend themselves from attacks by early whalers, occasionally resulting in the destruction of the whaling ships.

The Sperm Whale was designated as the Connecticutstate animal by the CT General Assembly in 1975. It was selected because of its specific contribution to the state's history and because of its present-day plight as an endangered species.[122]

Sperm whales are not the easiest of whales to watch, due to their long dive times and ability to travel long distances underwater. However, due to the distinctive look and large size of the whale, watching is increasingly popular. Sperm whale watchers often use hydrophones to listen to the clicks of the whales and locate them before they surface. Popular locations for sperm whale watching include the picturesque Kaikoura on New Zealand's South Island, Andenes and Tromsø in Arctic Norway; as well as the Azores, where the continental shelf is so narrow that whales can be observed from the shore,[59][123] and Dominica[124] where a long-term scientific research program, The Dominica Sperm Whale Project, has been in operating since 2005.[125]

a Until 1974 the species was generally known as P. catodon. In that year, however, Husson & Holthuis proposed that the correct name should be P. macrocephalus, the second name in the genus Physeter published by Linnaeus concurrently with P. catodon. This proposition was based on the grounds that the names were synonyms published simultaneously, and, therefore, the ICZN principle of "First Reviser" should apply. In this instance, it led to the choice of P. macrocephalus over P. catodon, a view re-stated in Holthuis, 1987. This has been adopted by most subsequent authors, although Schevill (1986 and 1987) argued that macrocephalus was published with an inaccurate description and that therefore only the species catodon was valid, rendering the principle of "First Reviser" inapplicable. At the present time, the name P. catodon is used in the Catalogue of Life. However, this is expected to be changed to follow the most recent version of ITIS, which has recently altered its usage from P. catodon to P. macrocephalus following L. B. Holthuis, and recent (2008) discussions with relevant experts (refer cited ITIS page for additional information).[4][126][127][128][129][130]

↑Davis, L, Gallman, R. & Gleiter, K. (1997). In Pursuit of Leviathan: Technology, Institutions, Productivity, and Profits in American Whaling, 1816-1906 (National Bureau of Economic Research Series on Long-Term Factors in Economic Dev), University of Chicago Press.

↑ 114.0114.1114.2114.3"Appendix I and Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.